1. Field of the Invention
The present invention relates to a weather strip for a motor vehicle, and more particularly to a weather strip to be attached around a sliding sun roof of the motor vehicle.
2. Description of the Prior Art
A sliding sun roof is installed in an opening of a roof panel so as to be slidable backwards and forwards with respect to the motor vehicle. The sliding sun roof is opened by sliding the sun roof backwards and retracting it below the roof panel. The weather strip is attached around the sliding sun roof so as to seal a gap between a peripheral edge of the sliding sun roof and a frame portion of the roof panel opening.
Such a weather strip generally has a downwardly oriented drip lip that extends from its lower portion. This drip lip is meant to guide water leaking through a gap between the weather strip and the frame portion into a drip channel provided in the roof panel so as to be positioned below the drip lip (Japanese unexamined Utility Model publication No. Sho 56-49622).
When the motor vehicle is driven at high speeds, a negative pressure is generated along a surface of the roof panel, thereby causing the sliding sun roof to be drawn outwardly.
Due to this outward force, the sliding sun roof, especially the front portion, is likely to be lifted up. This reduces the sealing force of the weather strip. As a result, air leaks from the inside of the vehicle to the outside thereof, and such an airflow creates an aspiration noise.
In order to prevent this noise generation, conventionally, a seal lip has been formed over the entire length of the weather strip outside the drip lip with the top end of the seal lip being brought into pressurized contact with the frame portion of the roof panel opening (Japanese unexamined Utility Model publication No. Sho 64-34328).
This seal lip acts as a resistive force to the outward drawing force acting on the sliding sun roof. Further, the seal lip prevents the sliding sun roof from being lifted. Even if the sliding sun roof is slightly lifted, the seal lip keeps contact with the frame portion with no reduction in the sealing force thereof.
However, this seal lip also acts to resist the backward and forward sliding movement of the sliding sun roof. Therefore, it has been the custom to cut off the seal lip by means of a cutter or the like, leaving only the front portion corresponding to the front end of the sliding sun roof, which is likely to be lifted up due to the outward force thereon (Japanese unexamined patent publication No. Hei 1-306321).
FIGS. 7 and 8 illustrate examples of the above-described prior art.
FIG. 7 illustrates a cross-section of the weather strip attached to the front end of a sliding sun roof, and FIG. 8 illustrates a corner portion of the weather strip attached to a corner of the sliding sun roof between the front end and the left side thereof.
The weather strip 2 has a drip lip 23 and a seal lip 24, both extending from the lower portion of a tubular sealing portion 22. This seal lip 24 is cut off except for the front portion corresponding to the front end of a sun roof 1 made of a glass plate. Reference numeral 25 (FIG. 8) designates a cut end of the seal lip 24.
In the front end of the sun roof 1, on which the outward force acts to lift up the front end at high motor vehicle speeds, the seal lip 24 comes into pressure contact with a frame portion 41 of a roof panel 4 to maintain an adequate seal and acts to resist lift of the sun roof 1.
In the side edges of the sun roof 1, the seal lip 24 of the weather strip 2 is removed. Accordingly, resistance to the sliding movement of the sliding sun roof is not increased therein.
However, it is extremely difficult to extrude the weather strip having two lips 23, 24 at closed positions while maintaining their precise dimensions. Moreover, it is also difficult work to partially cut off the seal lip 24 after extrusion by means of a cutter or the like. Therefore, the productivity of the prior art is not good.